A. Field of Invention
The present invention relates, in general, to a measuring device for repetitive and reproducible dispensing of quantitatively predetermined dosages of a liquid such as a medicine held in a container. More specifically, this invention relates to a tamper-resistant, child-resistant, plunger-type dropper assembly which allows variable dosage selectability without using springs or screw threads for plunger return.
B. Description of Related Art
Conventional containers are used to store and transport certain liquids, such as medicines, vitamins, and the like, which often have to be dispensed in small but precise quantities or dosages. Such dosages may be on the order of one milliliter or less and are characteristically dispensed using a pipette and compressible, resilient bulb dropper assembly.
It is often very difficult to draw the exact amounts of liquid in the minute quantities necessary using a conventional dropper assembly. Control of the assembly is especially difficult for relatively unskilled persons, such as consumers. This problem is particularly severe for elderly patients who are generally beset with ailments requiring medication. A brief explanation of the pipetting concept illustrates why such control is difficult.
The pipette, open at both ends, is placed at one end into the substantially air tight liquid container. The compressible bulb is mounted on top of the opposite end of the pipette. Such droppers are often incorporated into the cap or closure used to seal the container and retain the liquid. The pipette is affixed to the cap, usually mounted in the center of the cap in a sealed relationship. One end of the pipette depends into the container when the cap is screwed onto the container and the opposite end of the pipette extends above the cap into the bulb.
Whether a free dropper or a cap-mounted dropper is used, the pipette is first filled with liquid by compressing the bulb with the pipette immersed in the liquid. The bulb may be compressed mechanically with a plunger or by hand. This compression causes the air inside the bulb to expel from the bulb into the container. When the pressure exerted by the plunger or user on the bulb is released, the elasticity of the bulb allows it to return to its initial volume, creating a vacuum in the bulb. That vacuum allows liquid in the container to rise into the pipette. The assembly may then be unscrewed from the container and the liquid contained in the pipette dispensed by exerting anew pressure on the bulb.
Thus, the degree of vacuum created in the bulb is directly related to the amount of liquid drawn into the pipette and subsequently dispensed. It is very difficult to control the vacuum created, and therefore the dosage dispensed. This is true even though the pipette is usually graduated with markings indicating dosage amounts, because it is impossible to expect a smooth dispensing operation. The control problem is especially acute when the dropper is used in the dark or dimly illuminated rooms in which patients often reside.
With the above discussion in mind, it is one object of the present invention to provide a dropper system which allows the user to preselect a precise dosage and to deliver that precise dosage invariably and exactly.
There are devices available which allow the user to fix the depression distance of the bulb and, consequently, to preselect the volume of liquid drawn into the pipette. Few of these devices allow the user, however, to vary the preselected dosage. The ability to provide a variable dosage selectability feature is another object of the invention.
The few devices which do allow variable dosage selectability often require the user to replace one cap with another or one plunger with another of different length in order to achieve a fixed dosage. This requirement wastes user time and increases the cost of the device. Other devices require complex springs, screw threads, or camming mechanics. These requirements cause the devices to become complicated in construction and accordingly expensive.
Therefore, it is a further object of the present invention to provide a dropper system which allows the user to vary the precise dosage preselected without requiring replacement components or incorporating complex mechanics. A related object is to construct the system in a commensurately simple and economic fashion. Still another related object is to construct the system to incorporate a compact outer shape without projecting parts.
When a system allows the user to vary the preselected dosage, an inherent risk arises that the dosage selected may be inadvertently altered. For example, the extent of plunger travel and consequent compression of the bulb may be affected if the cap is mistakenly twisted. Accordingly, related objects of the invention are to (1) fix the preselected dosage once it is set by preventing inadvertent alteration, and (2) provide notice if the system is altered such that the dosage which will be dispensed has changed from that previously selected.
Although the use of a plunger-type pipette and bulb dropper assembly, which applies capillary flow concepts, is sound, the devices previously developed to incorporate plunger activation of the bulb have a common drawback: they do not assure that the plunger will contact the bulb at the center of the bulb. Unless the plunger contacts very nearly the center of the bulb, the bulb may topple over rather than compress symmetrically. Absent a consistent, symmetrical, accordion-like compression of the bulb, the system cannot provide a maximum, hence consistent, draw of liquid upon each use. Thus, still another object of the invention is to assure that the plunger contacts the center of the bulb.
Unfortunately, safety has recently, of necessity, become a high priority in the provision of consumer products including medicines, vitamins, and the like. Accordingly, another object of the invention is to provide a tamper resistant dropper system. Protection even against potential syringe-type injections in the dispensing bulb is within the scope of this object.
In order to further preclude tampering and to protect against even innocent damage to or loss of both the plunger and bulb, it is desirable to enclose these components within a protective housing. Still another object of the present invention is to provide a protective housing which permanently encloses the bulb and prevents complete removal of the plunger from the housing.
An object ancillary to the safety aspect of the two previous objects is to provide a child-resistant system, protecting against undesired opening of the container by small children who may be harmed by the liquid contents. A problem with many caps designed to make a container "child-proof" is the difficulty many adults have in opening them. Many designs require the user to squeeze the cap while twisting it. The force necessary to squeeze the rigid cap is difficult to apply for some users. Some adults afflicted, for example, with arthritis have trouble squeezing caps because their fingers or wrists may be sore. Still another object of this invention is to provide a child-resistant system which does not require a squeezing action for either opening or closing the container.
Finally, it is an object of the present invention to provide a system which uses standard dropper components: pipette, cap, and bulb. By achieving this object, the invention can be manufactured as a complete unit which incorporates such standard components into the system; the invention can also be manufactured for use with preexisting standard dropper systems.